Key Points
Nrp-1 expression is induced on a subset of CD4+Foxp3− T cells upon stimulation.
Stimulation-induced iNrp-1+CD4+Foxp3− T cells exhibit a highly activated phenotype.
Pre-existing nNrp-1+CD4+Foxp3− T cells from naive mice are dysfunctional.
Abstract
Neuropilin-1 (Nrp-1) is a well described marker molecule for CD4+Foxp3+ thymus-derived regulatory T cells (Tregs). In addition, a small population of CD4+Foxp3− conventional (conv) T cells expresses Nrp-1 in naive mice, and Nrp-1 expression has been described to be upregulated on activated CD4+ T cells. However, the function of Nrp-1 expression on CD4+ non-Tregs still remains elusive. In this study, we demonstrate that Nrp-1 expression was induced upon stimulation of CD4+Foxp3− T cells in vitro and during an ongoing immune response in vivo. This activation-induced Nrp-1+CD4+ T cell subset (iNrp-1+) showed a highly activated phenotype in terms of elevated CD25 and CD44 expression, enhanced production of proinflammatory cytokines, and increased proliferation compared with the Nrp-1−CD4+ counterpart. In contrast, Nrp-1+CD4+Foxp3− conv T cells from naive mice (nNrp-1+) were dysfunctional. nNrp-1+CD4+ conv T cells upregulated activation-associated molecules to a lesser extent, exhibited impaired proliferation and produced fewer proinflammatory cytokines than Nrp-1−CD4+ conv T cells upon stimulation in vitro. Moreover, the expression of PD-1 and CTLA-4 was significantly higher on nNrp-1+CD4+Foxp3− T cells compared with iNrp-1+CD4+Foxp3− T cells and Nrp-1−CD4+Foxp3− T cells after stimulation and under homeostatic conditions. Strikingly, transfer of Ag-specific iNrp-1+CD4+ conv T cells aggravated diabetes development, whereas Ag-specific nNrp-1+CD4+ conv T cells failed to induce disease in a T cell transfer model of diabetes. Overall, our results indicate that Nrp-1 expression has opposite functions in recently activated CD4+ non-Tregs compared with CD4+ non-Tregs from naive mice.
Footnotes
This work was supported by Deutsche Forschungsgemeinschaft grants to W.H., A.M.W., and J. Buer (RTG1949).
The online version of this article contains supplemental material.
- Received May 5, 2021.
- Accepted July 2, 2021.
- Copyright © 2021 by The American Association of Immunologists, Inc.
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